Intel lapse behind Shahzad being able to board the plane?

Times Square bombing suspect Faisal Shahzad's bid to flee the United States did not raise any red flag as the airline whose flight to Dubai he boarded had not refreshed its information on the Pakistani-American being tailed by the Federal Bureau of Investigation.

Shahzad was able to board Emirates Flight 202 late on Monday despite being put on a 'no-fly list' earlier in the day, but at the time of his ticket purchase, the airline had not refreshed its information so his name did not raise any red flag, CNN quoted a senior counter-terrorism official as saying.

Authorities had tailed Shahzad throughout the day, but lost him before he arrived at New York's John F Kennedy International Airport, where he was ultimately arrested, the official said.

However, an FBI official told the channel that surveillance operations are designed with redundancies in place, and that agents had to avoid tipping off Shahzad that he was being followed.

US Attorney General Eric Holder also defended surveillance efforts. "I was here all yesterday and through much of last night and was aware of the tracking that was going on, and I was never in any fear that we were in danger of losing him," Holder said.

But some US lawmakers are not fully convinced. A member of House of Representatives from New York, Charles Rangel noted that, along with Umar Abdulmutallab, a Nigerian man who tried to bring down a Northwest Airlines flight on Christmas Day, this is the second high-profile incident in recent memory where someone on the US no-fly list has managed to board a plane.

Shahzad, 30, was arrested shortly before midnight on Monday at JFK airport after US Customs and Border Protection, which reviews all flight manifests, caught his name when the airline sent the agency its passenger list, according to the counter-terrorism official.

Senator Susan Collins, a Republican from Maine and ranking member of the committee, also expressed concerns. "A key question for me is why this suspect was allowed to board the plane in the first place," Collins said, according to the New York Times.

"There appears to be a troubling gap between the time they had his name and the time he got on the plane." Pete Hoekstra, ranking member of the House Intelligence Committee, told CNN that US intelligence efforts have to be better.

"Being lucky can't be our national security strategy," Hoekstra said. "We were lucky on Christmas Day. We were lucky last week."